Solution

The correct answer is (C), (A), (B), (D)

EXPLANATION:

Steps in DHCP IP lease renewal:

• (C) DHCP client checks the local lease timer and initiates renewal:
  • A DHCP (Dynamic Host Configuration Protocol) client typically initiates a renewal process when 50% of its lease time has expired, though this can be configured differently. DHCP clients manage a lease timer which monitors the duration for which the allocated IP address is valid.
• (A) DHCP client sends a DHCPREQUEST message:
  • If the DHCP client determines that the lease is set to expire, it will request a lease renewal from the DHCP server. It does this by sending a DHCPREQUEST message to the server. This message contains the client's current IP address.
• (B) DHCP server acknowledges the renewal with a DHCPACK message:
  • The DHCP server receives the DHCPREQUEST message from the DHCP client. If the server determines that the request is valid and the IP address can be renewed, the server sends back a DHCPACK message to the client. This acknowledgement includes the renewed lease duration and any network configuration options that the server is set to distribute.
• (D) DHCP server updates its lease database:
  • Finally, after successfully renewing the client's lease, the DHCP server updates its own lease database to reflect this change. This is to keep track of all IP addresses it has leased out. It helps in future IP address allocation, ensuring that the DHCP server doesn't accidentally assign an already leased IP address to a different client.